Solid-state lighting (SSL) devices such as light emitting diode (LED) lighting devices attract much attention due to features such as low power consumption, long life and high luminance.
One of the significant elements of a lighting device is a dimmer for controlling the brightness of light, and recently TRIAC-based dimmers are frequently used (See Korean Patent No. 1055865).
In the above-described TRIAC-based dimmers, however, it is problematic that the load of the LED lighting device is too small to appropriately operate with the TRIAC dimmer. As such, the LED lighting device may flicker at a very low diming level or may even get permanently switched off. That is, when TRIAC dimmers are present, low power consumption of SSL devices may cause problems due to a latching and holding currents of the TRIAC dimmers.
In particular, lamps having low power consumption below 40 W (e.g., 2 W candle light bulb for E14 screw socket) do not reach the minimum load of a TRIAC dimmer. Accordingly, an operating current of the TRIAC dimmer drops below a holding current value and thus the LED lighting device may flicker and even may stop working.
That is, the minimum dimming level (MIN) includes a range in which a current flowing through a TRIAC dimmer drops below a holding current, and LED lighting device flickers in these periods.